"Quite often Sun-grazers or Sun-divers simply disintegrate - the head of the comet just evaporates because of the tremendous heat," says Hartley.

"Last Christmas, Comet Lovejoy was expected to be swallowed up when it got too close to the Sun, yet amazingly survived."

"This one's still an unknown, so we'll have to wait and see."

Expect the spectacular

Astronomers are speculating that C/2012S1 could be one of the brightest comets ever detected, easily visible in the northern hemisphere for several months as it approaches the Sun. Star watchers located south of the equator may only get a glimpse of its tail.

Some reports have suggested the comet could be as bright as magnitude -11 or even -16, making it more than 1000 times brighter than the planet Venus and almost as bright as a full Moon.

"It's an unknown," says Hartley. "It could be a dazzler or a complete washout, that's the problem with comets like this one."

If it survives its close encounter with the Sun, C/2012S1 will pass about 60 million kilometres from Earth on 26 December 2013.

Its orbit suggests C/2012S1 originated in the Oort Cloud, a distant comet repository a quarter of the way to the nearest star. But Hartley speculates that it could have previously passed by the Earth.

"There was a great comet in 1680 with an orbit very similar to this comet," he says. "So there's a faint possibility that it may be this comet [or part of it] coming back."

The Milky Way has up to three times more star-forming material than previously thought. Also; sudden dramatic increase in X-ray flares blasting out of supermassive black hole at the centre of our galaxy, and stunning new views of Enceladus.

Take a trip back into deep time with Dr Richard Smith in this amazing interactive documentary series